The present invention relates to a positive-working light-sensitive composition which permits production or formation of lithographic printing plates, proofs of multicolor printings, drawings for overhead projectors and fine resist patterns in preparing integrated circuits of semiconductor elements.
There have conventionally been proposed various kinds of so-called positive-working light-sensitive compositions which can be solubilized through irradiation with actinic light rays as materials for preparing, for instance, lithographic printing plates. For instance, (i) a light-sensitive composition comprising a natural polymer such as albumen or glue or polyvinyl alcohol and bichromate; (ii) a light-sensitive composition comprising an o-quinonediazide compound; and (iii) a light-sensitive composition comprising a diazonium salt have been known. However, the foregoing light-sensitive compositions each has merits and demerits and they are thus still insufficient.
The light-sensitive composition (i) is economically advantageous since its price is reasonable, but the composition has low storage stability and other problems concerning handling thereof such as discard thereof arise since a bichromate is used as a starting material.
The foregoing light-sensitive compositions (ii) comprising o-quinonediazide compounds are excellent materials for forming positive images and have, in fact, widely been used for preparing, for instance, lithographic printing plates.
These o-quinonediazide compounds are disclosed in various publications, for instance, U.S. Pat. Nos. 2,766,118; 2,767,092; 2,772,972; 2,859,112; 2,907,665; 3,046,110; 3,046,111, 3,046,115, 3,046,118; 3,046,119; 3,046,120; 3,046,121; 3,046,122; 3,046,123; 3,061,430; 3,102,809; 3,106,465; 3,635,709; and 3,647,443.
These o-quinonediazide compounds are decomposed through irradiation with actinic light rays to give 5-membered carboxylic acids and to thus be made alkaline-soluble, but have insufficient light-sensitivity. This is because photochemical sensitization is difficult depending on the kinds of o-quinonediazide compounds and the quantum yield thereof never exceeds 1. Moreover, they are only sensitive to light rays of specific wavelengths. Therefore, they are insufficiently adapted for light sources and it is difficult to make them insensitive to white light. In addition, they greatly absorb light rays in the Deep UV region and, therefore, are not adapted for applications in which light rays of short wavelengths are used for improving the resolution of photoresists.
Various methods for eliminating these disadvantages have been proposed (see, for instance, Japanese Patent Publication for Opposition Purpose (hereinafter referred to as "J.P. KOKOKU") No. Sho 48-12242 (U.S. Pat. No. 3,661,582), Japanese Unexamined Patent Publication (hereinafter referred to as "J.P. KOKAI") No. Sho 52-40125 (U.S. Pat. No. 4,009,033) and U.S. Pat. No. 4,307,173), but the improvement is still insufficient.
Examples of the foregoing positive-working light-sensitive composition (iii) comprising a diazo compound are those disclosed in, for instance, U.S. Pat. Nos. 3,219,447 and 3,211,533, J.P. KOKOKU No. Sho 39-7663 and J.P. KOKAI No. Sho 52-2519, but they have low sensitivity and do not stably form images. Thus, they have been impracticable.
Alternatively, there have recently been proposed several compounds as new light-sensitive materials used in place of these positive-working light-sensitive compounds. One example thereof is a polymeric compound carrying o-nitrocarbinol ester groups as disclosed in J.P. KOKOKU No. Sho 56-2696 (U.S. Pat. No. 3,849,137). However, these compounds are still insufficient in sensitivity.
On the other hand, a photoresist has generally been used for forming a pattern in a method for producing electronic parts such as semiconductor elements, magnetic bubble memories and integrated circuits. Photoresists are divided into negative-working ones which are made insoluble in a developer through irradiation with light rays and positive-working ones which are, on the contrary, made soluble in a developer through irradiation with light rays. The negative-working photoresist has been one of mainstreams of photoresists till quite recently because of good sensitivity, excellent adhesion to a substrate which is favorable for the wet etching and high resistance to chemicals as compared with the positive-working photoresists. However, the formation of fine patterns (minute line widths and spaces between lines) has been required as the package density and degree of integration of semiconductor elements or the like have been increased and the dry etching technique has been used for etching substrates. These situations require that photoresists must have high resolution and high resistance to dry etching and accordingly, positive-working photoresists have recently been one of the mainstreams of photoresists. Among positive-working photoresists, those presently widely used are alkaline-developable positive-working photoresists mainly comprising alkali-soluble novolak resins as disclosed in, for instance, J. C. Strieter, Kodak Microelectronics Seminar Proceedings, 1976, p. 116 because of excellent sensitivity, resolution and resistance to dry etching.
However, there has intensity been required for making patterns more finer to further increase the package density and degree of integration and to respond to the demand for multifunctionalization of the recent electronic equipments and improvement of sensitivity thereof. To meet these requirements, there have been proposed light-sensitive composition comprising conventional o-quinonediazide light-sensitive compounds in combination with polysiloxanes which are made alkali-soluble or silicone polymers such as polysilmethylene, for instance, light-sensitive compositions such as those disclosed in, for instance, J.P. KOKAI Nos. Sho 61-256347, Sho 61-144639, Sho 62-159141, Sho 62-191849, Sho 62-220949, Sho 62-229136, Sho 63-90534 and Sho 63-91654 and a light-sensitive composition comprising a polysiloxane/carbonate block copolymer and an effective amount of an onium salt disclosed in J.P. KOKAI No. Sho 62-136638. However, these silicone polymers must be made alkaline-soluble. This makes the production thereof very difficult. Further, they have insufficient stability with time.